Heat exchanger and refrigeration cycle apparatus

ABSTRACT

In a heat exchanger, when a lower surface of the first heat transfer tube is horizontal, in a vertical cross section perpendicular to a direction in which the first heat transfer tube passes through a first fin, upper surfaces of the first and second heat transfer tubes are inclined downward, an upper end of the second heat transfer tube is higher than the lower surface of the first heat transfer tube, and an intersecting point A at which an extension line of the upper surface of the second heat transfer tube and an extension line of the lower surface of the first heat transfer tube intersect is closer to the second heat transfer tube than is an intersecting point B at which the extension line of the upper surface of the second heat transfer tube and an extension line of a lower surface of the second heat transfer tube intersect.

TECHNICAL FIELD

The present invention relates to a heat exchanger in which both ofdrainage performance and heat transfer performance are improved, and arefrigeration cycle apparatus including the same.

BACKGROUND ART

An existing heat exchanger has been known in which two or morefin-and-tube type heat exchanging parts are arranged in parallel along aflow direction of air blown out in a lateral direction from a fan. Morespecifically, each of the heat exchanging parts of this heat exchangerincludes a plurality of fins extending in an up-down direction and aplurality of heat transfer tubes. The plurality of fins are arranged inparallel at a predetermined interval in the lateral directionsubstantially perpendicular to the air flow direction. The plurality ofheat transfer tubes are arranged in parallel at a predetermined intervalin the up-down direction and pass through the fins along an arrangementdirection of these fins. Ends of each of the heat transfer tubes areconnected to distribution pipes or headers to form refrigerant passagesincluding these heat transfer tubes. In the heat exchanger, heat isexchanged between the air flowing into gaps between the fins and therefrigerant flowing through the heat transfer tubes.

The heat exchanger configured as described above is also proposed inwhich a flat tube is used as the heat transfer tube. The flat tube is aheat transfer tube that has, for example, an elliptical sectional shapein which the width is larger than the height in a cross-sectional viewperpendicular to the flow direction of the refrigerant. Compared withthe heat exchanger including circular tubes, the heat exchangerincluding the flat tubes can ensure a large area of heat transfer of thetubes and reduce the ventilation resistance of the air. Thus, comparedwith the heat exchanger including circular tubes, the heat exchangerincluding the flat tubes can provide improved heat transfer performance.In contrast, when the heat exchanger including the flat tubes is used asan evaporator, its drainage performance is inferior to that of the heatexchanger including circular tubes. This is because water dropletsreadily stay on the upper surfaces of the flat tubes.

For example, when in an air-conditioning apparatus and a refrigerationcycle apparatus such as a freezer, the heat exchanger for an outdoorunit is used as an evaporator at low outside air temperature, the waterin the air condenses and forms frost on the heat exchanger. The frostformation leads to an increase in the ventilation resistance, impairmentin the heat transfer performance, and damage to the heat exchanger. Toavoid these problems, a typical refrigeration cycle apparatus has adefrosting operation mode for melting frost adhering to the heatexchanger. As described above, the water droplets readily stay on theheat exchanger including the flat tubes. When the water droplets stay onthe heat exchanger, the water droplets freeze and form a large volume offrost. That is, the heat exchanger including the flat tubes requires alonger period of defrosting operation, resulting in impairment incomfortability and a reduction in average heating capacity.

Patent Literature 1 discloses that in a heat exchanger in which twofin-and-tube type heat exchanging parts using flat tubes having anelliptical sectional shape are arranged in parallel along a flowdirection of air blown out in a lateral direction from a fan, the flattubes are arranged in such a manner that the upper surfaces of the flattubes are inclined.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. 2007-183088

SUMMARY OF INVENTION Technical Problem

In the heat exchanger disclosed in Patent Literature 1, the uppersurface of each of the flat tubes is inclined to cause condensed waterdroplets staying on the upper surfaces of the flat tubes to be readilydrained off by the gravity. Consequently, the heat exchanger disclosedin Patent Literature 1 can reduce the period of defrosting operation. Incontrast, the heat exchanger disclosed in Patent Literature 1 cannotexert the sufficient heat transfer performance, which is an advantage ofthe flat tubes.

More specifically, the air that has flowed into the heat exchangerreaches the leading edge of the flat tube and splits into two ways, thatis, the way along the upper surface and the way along the lower surfaceof the flat tube. On the surface oriented to face the air flow, the airflows along the tube wall, and passes through the heat exchanger whilemaintaining the relatively high air velocity. On the other hand, on thesurface that does not face the air flow, the air hardly flows along thetube wall, thereby causing the stagnation of the air flow, that is, adead water region. When the heat exchanger disclosed in PatentLiterature 1 is viewed in the air flow direction, the flat tubes of theheat exchanging part located downstream in the air flow direction arearranged behind the dead water region of the flat tubes of the heatexchanging part located upstream. Consequently, sufficient amount of airdoes not flow in the vicinity of the surfaces of the flat tubes of theheat exchanging part located downstream in the air flow direction,thereby causing a reduction in air velocity at such a position. As aresult, the heat exchanger disclosed in Patent Literature 1 cannot exertthe sufficient heat transfer performance, which is an advantage of theflat tubes.

As one method for solving the problem, it is proposed that thearrangement positions of the flat tubes located downstream in the airflow direction are changed in such a manner that the flat tubes locateddownstream are not located behind the flat tubes located upstream whenthe heat exchanger is viewed in the air flow direction. That is, it isproposed that the flat tubes located downstream are arranged not tooverlap with the flat tubes located upstream when the heat exchanger isviewed in the air flow direction. However, in the heat exchanger thusconfigured, the ventilation resistance of the heat exchanger isincreased, thereby causing impairment in the heat transfer performance.

An object of the present invention is to provide a heat exchanger inwhich both of drainage performance and heat transfer performance areimproved, and a refrigeration cycle apparatus including the same.

Solution to Problem

A heat exchanger of an embodiment of the present invention includes afirst fin having a first end and a second end in a lateral direction, asecond fin having a third end and a fourth end in the lateral direction,the third end being positioned to face the second end, a first heattransfer tube positioned away from the first end by a firstpredetermined interval and passing through the first fin, and a secondheat transfer tube positioned away from the third end by a secondpredetermined interval and passing through the second fin. The firstheat transfer tube has a planar or curved first upper surface and aplanar first lower surface, the second heat transfer tube has a planaror curved second upper surface and a planar second lower surface, whenthe first upper surface is defined as a first surface in a case wherethe first upper surface has a planar shape, a tangent plane of the firstupper surface is defined as a first surface in a case where the firstupper surface has a curved shape, the second upper surface is defined asa second surface in a case where the second upper surface has a planarshape, and a tangent plane of the second upper surface is defined as asecond surface in a case where the second upper surface has a curvedshape, and when the first heat transfer tube and the second heattransfer tube are viewed in such a manner that the first lower surfaceis horizontal, in a vertical cross section perpendicular to a directionin which the first heat transfer tube passes through the first fin, thefirst surface is inclined downward toward the first end, the secondsurface is inclined downward toward the third end, an upper end of thesecond heat transfer tube is located higher than the first lowersurface, and an intersecting point A at which the second surface or anextension line of the second surface and an extension line of the firstlower surface intersect coincides with an intersecting point B at whichthe second surface or the extension line of the second surface and anextension line of the second lower surface intersect, or is locatedcloser to the second heat transfer tube than is the intersecting pointB.

A refrigeration cycle apparatus of an embodiment of the presentinvention includes the heat exchanger of an embodiment of the presentinvention, and a fan configured to supply air to the heat exchanger fromthe first end along the first lower surface. The heat exchanger isinstalled in such a manner that the first surface is inclined downwardtoward the first end, and the second surface is inclined downward towardthe third end.

Advantageous Effects of Invention

An embodiment of the present invention provides a heat exchanger inwhich both of drainage performance and heat transfer performance areimproved, and a refrigeration cycle apparatus including the same.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a refrigerant circuit of arefrigeration cycle apparatus according to Embodiment 1 of the presentinvention.

FIG. 2 is a front view illustrating a heat exchanger according toEmbodiment 1 of the present invention.

FIG. 3 is an enlarged view (front view) illustrating a main portion offins of the heat exchanger according to Embodiment 1 of the presentinvention.

FIG. 4 is a cross-sectional view illustrating a heat transfer tube ofthe heat exchanger according to Embodiment 1 of the present invention.

FIG. 5 is an enlarged view of a main portion of a part of FIG. 2.

FIG. 6 is a front view illustrating a heat exchanger according toEmbodiment 2 of the present invention.

FIG. 7 is an enlarged view (front view) illustrating a main portion offins of the heat exchanger according to Embodiment 2 of the presentinvention.

FIG. 8 is an enlarged view of a main portion of a part of FIG. 6.

FIG. 9 is a front view illustrating a heat exchanger according toEmbodiment 3 of the present invention.

FIG. 10 is an enlarged view (front view) illustrating a main portion offins of the heat exchanger according to Embodiment 3 of the presentinvention.

FIG. 11 is an enlarged view of a main portion of a part of FIG. 9.

FIG. 12 is a front view illustrating a heat exchanger according toEmbodiment 4 of the present invention.

FIG. 13 is an enlarged view (front view) illustrating a main portion offins of the heat exchanger according to Embodiment 4 of the presentinvention.

FIG. 14 is an enlarged view of a main portion of a part of FIG. 12.

DESCRIPTION OF EMBODIMENTS

Embodiments of a heat exchanger and a refrigeration cycle apparatusaccording to the present invention will be described hereinafter withreference to the drawings.

Embodiment 1

FIG. 1 is a diagram illustrating a refrigerant circuit of arefrigeration cycle apparatus according to Embodiment 1 of the presentinvention.

A refrigeration cycle apparatus 100 includes a compressor 200, acondenser 300, an expansion mechanism 400, and an evaporator 500. Thesecomponents of the refrigeration cycle apparatus 100 are sequentiallyconnected through refrigerant pipes.

The compressor 200 is configured to suck refrigerant and compress thesucked refrigerant into high-temperature and high-pressure gasrefrigerant. The condenser 300 is configured to exchange heat betweenthe refrigerant flowing through the condenser 300 and air or otherheat-exchanging target. The condenser 300 is, for example, a fin-tubetype heat exchanger. A fan 301 configured to supply the air serving asheat-exchanging target to the condenser 300 is provided in the vicinityof the condenser 300. The expansion mechanism 400 is, for example, anexpansion valve, and is configured to decompress and expand therefrigerant. The evaporator 500 is configured to exchange heat betweenthe refrigerant flowing through the evaporator 500 and air or otherheat-exchanging target. The evaporator 500 according to Embodiment 1 isa fin-tube type heat exchanger. A fan 501 configured to supply the airserving as heat-exchanging target to the evaporator 500 is provided inthe vicinity of the evaporator 500. The fan 501 is, for example, apropeller fan.

In the refrigeration cycle apparatus 100 according to Embodiment 1, aheat exchanger 1 having the following configuration is used as theevaporator 500 to improve both of the drainage performance and the heattransfer performance of the evaporator 500.

FIG. 2 is a front view illustrating a heat exchanger according toEmbodiment 1 of the present invention. FIG. 3 is an enlarged view (frontview) illustrating a main portion of fins of this heat exchanger. FIG. 4is a cross-sectional view illustrating a heat transfer tube of this heatexchanger. FIG. 5 is an enlarged view of a main portion of a part ofFIG. 2.

FIG. 2 illustrates heat transfer tubes 15 and 25 in cross section. Ablank arrow shown in each of FIG. 2 and FIG. 5 represents a flowdirection of air to be supplied to the heat exchanger 1 from the fan501. That is, in Embodiment 1, the fan 501 is configured to supply airto the heat exchanger 1 in a substantially horizontal direction. Inother words, a rotary shaft of the fan 501, which is a propeller fan, ispositioned in the substantially horizontal direction. In each of FIGS.2, 3, and 5, this air flow direction is also represented by an arrow X.An arrow Z shown in each of FIGS. 2, 3, and 5 represents the gravitydirection.

In the heat exchanger 1, a plurality of fin-and-tube type heatexchanging parts are arranged in parallel along the air flow direction.In Embodiment 1, the description focuses on an example in which the heatexchanger 1 includes a first heat exchanging part 10 located upstream ofthe air flow direction, and a second heat exchanging part 20 locateddownstream of the air flow direction. The first heat exchanging part 10and the second heat exchanging part 20 have a similar configuration.

More specifically, the first heat exchanging part 10 includes aplurality of plate-shaped fins 11 extending in the up-down direction.These fins 11 are arranged in parallel at a predetermined fin pitch(interval) in a lateral direction perpendicular to the air flowdirection (a direction perpendicular to the paper plane of FIG. 2). Aplurality of notches 12 are cut in a downstream end 11 d of each of thefins 11 at a predetermined tier pitch (space) in the up-down direction.These notches 12 are cut so that the respective heat transfer tubes 15are to be inserted into the notches, and have a shape corresponding toan outer shape of the heat transfer tube 15. An upstream end 12 a ofeach of the notches 12 is positioned away from an upstream end 11 c ofthe fin 11 by a predetermined interval (a first predetermined interval).Each of the notches 12 has a shape in such a manner that a distancebetween an upper edge and a lower edge of the notch 12 is graduallyincreased from the upstream end 12 a to an opening 12 b. Consequently,the heat transfer tubes 15 can be readily inserted into the respectivenotches 12.

Here, the fin 11 corresponds to a first fin of the present invention.The upstream end 11 c corresponds to a first end of the presentinvention. The downstream end 11 d corresponds to a second end of thepresent invention.

The first heat exchanging part 10 includes a plurality of heat transfertubes 15 inserted into the respective notches 12 in each of the fins 11.That is, the heat transfer tubes 15 are arranged in parallel at apredetermined tier pitch in the up-down direction. Each of the heattransfer tubes 15 is provided to pass through the fins 11 in anarrangement direction of these fins 11. The fins 11 and the heattransfer tubes 15 are tightly integrated with each other by brazing.Each of these heat transfer tubes 15 has a larger width than height in across-sectional view perpendicular to the flow direction of therefrigerant. Each of the heat transfer tubes 15 accommodates a pluralityof partitions, which define a plurality of refrigerant passages 16inside the heat transfer tube 15.

The shape of the heat transfer tube 15 will be further described indetail. The heat transfer tube 15 has a planar upper surface 15 a and aplanar lower surface 15 c. A distance between the upper surface 15 a andthe lower surface 15 c is gradually increased from the upstream end 15 btoward the downstream end 15 d. In other words, the distance between theupper surface 15 a and the lower surface 15 c is gradually increasedfrom the upstream end 11 c toward the downstream end 11 d of the fin 11.Such a heat transfer tube 15 is made of, for example, aluminum or analuminum alloy, and is fabricated by, for example, extrusion molding.Thus, in Embodiment 1, the heat transfer tube 15 accommodatespartitions, which define a plurality of refrigerant passages 16 insidethe heat transfer tube 15, in such a manner that the upper surface 15 aand the lower surface 15 c are substantially symmetrical to a planeincluding a bisector of an angle formed by the upper surface 15 a andthe lower surface 15 c. This shape can readily ensure themanufacturability in extrusion molding of the heat transfer tube 15. Theheat transfer tube 15 may be fabricated by, for example, extrusionmolding to have an elliptical sectional shape and then transformed intoa final shape by an additional process such as a press. The wallsurfaces of the refrigerant passages 16, that is, the inner wallsurfaces of the heat transfer tube 15 may have grooves. This structureincreases the area of contact between the inner wall surfaces of theheat transfer tube 15 and the refrigerant. The efficiency of heatexchange is improved, accordingly.

Here, any one of the heat transfer tubes 15 corresponds to a first heattransfer tube. The upper surface 15 a of the heat transfer tube 15corresponding to the first heat transfer tube corresponds to a firstsurface of the present invention.

As described above, the upstream ends 12 a of the respective notches 12,into which the respective heat transfer tubes 15 are to be inserted, ineach of the fins 11 are positioned away from the upstream end 11 c ofthe fin 11 by the predetermined interval (the first predeterminedinterval). Consequently, in a state in which the heat transfer tubes 15are fitted into the fin 11, the upstream ends 15 b of the respectiveheat transfer tubes 15 are also positioned away from the upstream end 11c of the fin 11 by the predetermined interval (the first predeterminedinterval). Such an arrangement enables each of the fins 11 to have afirst area 11 a and a second area 11 b. The first area 11 a is an areain which a plurality of notches 12 are cut in a longitudinal directioncorresponding to the gravity direction (represented by the arrow Z), andthe heat transfer tubes 15 are provided. The second area 11 b is an areain which no heat transfer tubes 15 are provided in the longitudinaldirection (represented by the arrow Z), and is a water drainage area fordraining off the water adhering to the fin 11. The second area 11 b ispositioned upstream of the first area 11 a in the flow direction(represented by the arrow X) of air serving as heat exchange fluid. Theboundary between the first area 11 a and the second area 11 b is avirtual straight line connecting the upstream ends 12 a of therespective notches 12 arranged in parallel in the up-down direction, inother words, a virtual straight line connecting the upstream ends 15 bof the respective heat transfer tubes 15 arranged in parallel in theup-down direction.

In the state in which the heat transfer tubes 15 are fitted into the fin11, each of the upper surfaces 15 a of the respective heat transfertubes 15 is inclined downward from the downstream end 11 d toward theupstream end 11 c of the fin 11, in other words, toward the second area11 b, which is the water drainage area. That is, the upper surface 15 aof the heat transfer tube 15 is inclined downward toward the upstreamend 11 c of the fin 11. In Embodiment 1, the upper surface 15 a of theheat transfer tube 15 is inclined by an angle θ to the horizontalsurface. On the other hand, in the state in which the heat transfertubes 15 are fitted into the fin 11, each of the lower surfaces 15 c ofthe respective heat transfer tubes 15 is substantially horizontal.

The second heat exchanging part 20 includes a plurality of plate-shapedfins 21 extending in the up-down direction. These fins 21 are arrangedin parallel at a predetermined fin pitch (interval) in a lateraldirection perpendicular to the air flow direction (a directionperpendicular to the paper plane of FIG. 2). A plurality of notches 22are cut in a downstream end 21 d of each of the fins 21 at apredetermined tier pitch (space) in the up-down direction. These notches22 are cut so that the respective heat transfer tubes 25 are to beinserted into the notches 22, and have a shape corresponding to an outershape of the heat transfer tube 25. An upstream end 22 a of each of thenotches 22 is positioned away from an upstream end 21 c of each of thefins 21 by a predetermined interval (a second predetermined interval).Each of the notches 22 has a shape in such a manner that a distancebetween an upper edge and a lower edge of the notch 22 is graduallyincreased from the upstream end 22 a to an opening 22 b. Consequently,the heat transfer tube 25 can be readily inserted into the correspondingnotch 22.

Here, the fin 21 corresponds to a second fin of the present invention.The upstream end 21 c corresponds to a third end of the presentinvention. The downstream end 21 d corresponds to a fourth end of thepresent invention.

The second heat exchanging part 20 includes a plurality of heat transfertubes 25 inserted into the respective notches 22 in each of the fins 21.That is, the heat transfer tubes 25 are arranged in parallel at apredetermined tier pitch in the up-down direction. Each of the heattransfer tubes 25 is provided to pass through the fins 21 in anarrangement direction of these fins 21. The fins 21 and the heattransfer tubes 25 are tightly integrated with each other by brazing.Each of these heat transfer tubes 25 has a larger width than height in across-sectional view perpendicular to the flow direction of therefrigerant. Each of the heat transfer tubes 25 accommodates a pluralityof partitions, which define a plurality of refrigerant passages 26inside the heat transfer tube 25.

The shape of the heat transfer tube 25 will be further described indetail. The heat transfer tube 25 has a planar upper surface 25 a and aplanar lower surface 25 c. A distance between the upper surface 25 a andthe lower surface 25 c is gradually increased from the upstream end 25 btoward the downstream end 25 d. In other words, the distance between theupper surface 25 a and the lower surface 25 c is gradually increasedfrom the upstream end 21 c toward the downstream end 21 d of the fin 21.Such a heat transfer tube 25 is made of, for example, aluminum or analuminum alloy, and is fabricated by, for example, extrusion molding.Thus, in Embodiment 1, the heat transfer tube 25 accommodatespartitions, which define a plurality of refrigerant passages 26 insidethe heat transfer tube 25 in such a manner that the upper surface 25 aand the lower surface 25 c are substantially symmetrical to a planeincluding a bisector of an angle formed by the upper surface 25 a andthe lower surface 25 c. This shape can readily ensure themanufacturability in extrusion molding of the heat transfer tube 25. Theheat transfer tube 25 may be fabricated by, for example, extrusionmolding to have an elliptical sectional shape and then transformed intoa final shape by an additional process such as a press. The wallsurfaces of the refrigerant passages 26, that is, the inner wallsurfaces of the heat transfer tube 25 may have grooves. This structureincreases the area of contact between the inner wall surfaces of theheat transfer tube 25 and the refrigerant. The efficiency of heatexchange is improved, accordingly.

Here, the heat transfer tube 25 laterally adjacent to the heat transfertube 15 corresponding to the first heat transfer tube corresponds to asecond heat transfer tube of the present invention. The upper surface 25a of the heat transfer tube 25 corresponding to the second heat transfertube corresponds to a second surface of the present invention.

As described above, the upstream ends 22 a of the respective notches 22,into which the respective heat transfer tubes 25 are to be inserted, ineach of the fins 21 are positioned away from the upstream end 21 c ofthe fin 21 by the predetermined interval (the second predeterminedinterval). Consequently, in a state in which the heat transfer tubes 25are fitted into the fin 21, the upstream ends 25 b of the respectiveheat transfer tubes 25 are also positioned away from the upstream end 21c of the fin 21 by the predetermined interval (the second predeterminedinterval).

Such an arrangement enables each of the fins 21 to have a first area 21a and a second area 21 b. The first area 21 a is an area in which aplurality of notches 22 are cut in a longitudinal directioncorresponding to the gravity direction (represented by the arrow Z), andthe heat transfer tubes 25 are provided. The second area 21 b is an areain which no heat transfer tubes 25 are provided in the longitudinaldirection (represented by the arrow Z), and is a water drainage area fordraining off the water adhering to the fin 21. The second area 21 b ispositioned upstream of the first area 21 a in the flow direction(represented by the arrow X) of air serving as heat exchange fluid. Theboundary between the first area 21 a and the second area 21 b is avirtual straight line connecting the upstream ends 22 a of therespective notches 22 arranged in parallel in the up-down direction, inother words, a virtual straight line connecting the upstream ends 25 bof the respective heat transfer tubes 25 arranged in parallel in theup-down direction.

In the state in which the heat transfer tubes 25 are fitted into the fin21, each of the upper surfaces 25 a of the respective heat transfertubes 25 is inclined downward from the downstream end 21 d toward theupstream end 21 c of the fin 21, in other words, toward the second area21 b, which is the water drainage area. That is, the upper surface 25 aof the heat transfer tube 25 is inclined downward toward the upstreamend 21 c of the fin 21. In Embodiment 1, the upper surface 25 a of theheat transfer tube 25 is inclined by an angle θ to the horizontalsurface. On the other hand, in the state in which the heat transfertubes 25 are fitted into the fin 21, each of the lower surfaces 25 c ofthe respective heat transfer tubes 25 is substantially horizontal.

The first heat exchanging part 10 and the second heat exchanging part 20configured as described above are arranged in such a manner that thedownstream ends 11 d of the respective fins 11 of the first heatexchanging part 10 and the upstream ends 21 c of the respective fins 21of the second heat exchanging part 20 face each other. Even when thefins 11 of the first heat exchanging part 10 and the fins 21 of thesecond heat exchanging part 20 are displaced from each other in thedirection perpendicular to the paper plane of FIG. 2, in Embodiment 1,the downstream ends 11 d of the respective fins 11 of the first heatexchanging part 10 are each construed as facing the corresponding one ofthe upstream ends 21 c of the respective fins 21 of the second heatexchanging part 20.

In the heat exchanger 1 according to Embodiment 1, the heat transfertubes 15 of the first heat exchanging part 10 and the heat transfertubes 25 of the second heat exchanging part 20, the heat transfer tubes25 being laterally adjacent to the respective heat transfer tubes 15,are provided in an arrangement relationship as illustrated in FIG. 5illustrating a vertical cross section perpendicular to the direction inwhich the heat transfer tubes 15 pass through the fins 11, in otherwords, as illustrated in FIG. 5 illustrating a vertical cross sectionperpendicular to the direction in which the heat transfer tubes 25 passthrough the fins 21. To describe this arrangement relationship indetail, intersecting points A and B are defined as follows. Anintersecting point at which an extension line of the second surface ofthe present invention (the upper surface 25 a of the heat transfer tube25 in Embodiment 1) or the second surface and an extension line of thelower surface 15 c of the heat transfer tube 15 intersect is defined asthe intersecting point A. An intersecting point at which the extensionline of the second surface of the present invention (the upper surface25 a of the heat transfer tube 25 in Embodiment 1) or the second surfaceand an extension line of the lower surface 25 c of the heat transfertube 25 intersect is defined as the intersecting point B.

More specifically, the upper end (a point C in FIG. 5) of the heattransfer tube 25 is located higher than the lower surface 15 c of theheat transfer tube 15 laterally adjacent to the heat transfer tube 25.The intersecting point A at which the upper surface 25 a of the heattransfer tube 25 and the extension line of the lower surface 15 c of theheat transfer tube 15 intersect is located closer to the heat transfertube 25 than is the intersecting point B at which the extension line ofthe upper surface 25 a and the extension line of the lower surface 25 cof the heat transfer tube 25 intersect. That is, the intersecting pointA is located downstream of the intersecting point B in the air flowdirection. In such an arrangement relationship, the heat transfer tube15 of the first heat exchanging part 10 and the heat transfer tube 25 ofthe second heat exchanging part 20, the heat transfer tube 25 beinglaterally adjacent to the heat transfer tube 15, overlap with each otherwhen the heat exchanger 1 is viewed in the air flow direction. In thearrangement relationship between the heat transfer tube 15 and the heattransfer tube 25 that overlap with each other when the heat exchanger 1is viewed in the air flow direction, the heat transfer tube 25 islocated slightly lower than the heat transfer tube 15.

Subsequently, the operation of the heat exchanger 1 according toEmbodiment 1 will be described.

First, the heat exchanging action between the air supplied from the fan501 and the refrigerant flowing in the heat transfer tubes 15 and 25will be described.

As described above, the fan 501 is, for example, a propeller fan, andthe rotary shaft of the fan 501 is positioned in the substantiallyhorizontal direction. As represented by the blank arrow in each of FIGS.2 and 5, the air supplied from the fan 501 flows in the substantiallyhorizontal direction into the heat exchanger 1 from the upstream end 11c of the fin 11 of the first heat exchanging part 10. This air flowsinto the first heat exchanging part 10, and then flows out through thesecond heat exchanging part 20.

More specifically, the air supplied from the fan 501 flows into gapsbetween the fins 11 of the first heat exchanging part 10 from theupstream ends 11 c of the respective fins 11. When this air reaches theupstream end 15 b of the heat transfer tube 15, the air splits into twoways, that is, the way along the upper surface 15 a and the way alongthe lower surface 15 c.

As described above, the upper surface 15 a of the heat transfer tube 15is inclined downward toward the upstream end 11 c of the fin 11. Thatis, the upper surface 15 a of the heat transfer tube 15 is oriented toface the air flow. Thus, the air can flow along the upper surface 15 aacross the majority of the heat transfer tube 15 in the width direction.Thus, the air flow without significant separation can facilitate heatexchange between the air and the heat transfer tube 15, and can alsoreduce the ventilation resistance.

As described above, the lower surface 15 c of the heat transfer tube 15is substantially horizontal. That is, the direction of the lower surface15 c of the heat transfer tube 15 substantially coincides with the airflow direction. Thus, the air can flow along the lower surface 15 cacross substantially the entire heat transfer tube 15 in the widthdirection. Thus, the air flow without significant separation canfacilitate heat exchange between the air and the surface of the heattransfer tube 15, and can also reduce the ventilation resistance.

When the attention is focused on the heat transfer tubes 15 adjacent toeach other in the up-down direction, a gap between the lower surface 15c of the heat transfer tube 15 located higher and the upper surface 15 aof the heat transfer tube 15 located lower narrows in the downstreamdirection of the air flow. This configuration can reduce creation of alow air velocity region (a dead water region) between the upper surfaceand the lower surface due to expansion of air passage, and canfacilitate heat exchange between the air and the surface of the firstheat exchanging part 10.

The air that has flowed around the heat transfer tubes 15 flows out ofthe first heat exchanging part 10 from the downstream ends 11 d of therespective fins 11. Here, in each of the heat transfer tubes 15 of thefirst heat exchanging part 10, the upper surface 15 a is inclineddownward toward the upstream end 11 c, and the lower surface 15 c issubstantially horizontal. The air flowing between the heat transfertubes 15 adjacent to each other in the up-down direction flows moreupward than the horizontal direction.

The air that has flowed out of the first heat exchanging part 10 flowsinto gaps between the fins 21 of the second heat exchanging part 20 fromthe upstream ends 21 c of the respective fins 21. When this air reachesthe upstream end 25 b of the heat transfer tube 25, the air splits intotwo ways, that is, the way along the upper surface 25 a and the wayalong the lower surface 25 c.

The upper surface 25 a of the heat transfer tube 25 is located behindthe downstream end 15 d of the heat transfer tube 15 located upstream ofthe heat transfer tube 25, in the air flow direction. That is, accordingto an existing art, the upper surface 25 a of the heat transfer tube 25is located behind the dead water region, resulting that sufficientamount of air cannot flow through the upper surface 25 a, therebyreducing the air velocity and the efficiency of heat exchange. However,in Embodiment 1, the air flowing into gaps between the fins 21 flowsmore upward than the horizontal direction, and reaches the upstream ends25 b of the respective heat transfer tubes 25. Consequently, asrepresented by an arrow W illustrated in FIG. 5, a part of air that hasreached the upstream end 25 b of the heat transfer tube 25 can flowalong the upper surface 25 a. This configuration can facilitate heatexchange between the air and the upper surface 25 a. In Embodiment 1,the upstream end 25 b of the heat transfer tube 25 is located slightlylower than the heat transfer tube 15. Thus, the amount of air flowingalong the upper surface 25 a of the heat transfer tube 25 can beincreased, thereby facilitating heat exchange between the air and theupper surface 25 a.

On the other hand, as the air that has reached the upstream end 25 b ofthe heat transfer tube 25 flows more upward than the horizontaldirection, the lower surface 25 c of the heat transfer tube 25 isoriented to face the air flow. Consequently, the air can flow along thelower surface 25 c of the heat transfer tube 25. This configuration canfacilitate heat exchange between the air and the lower surface 25 c.

Next, the water draining action of draining off water droplets adheringto the heat exchanger 1 will be described.

The water draining action of the first heat exchanging part 10 isdescribed below.

The water droplets adhering to the first area 11 a of each of the fins11 of the first heat exchanging part 10 flow along the surface of thefin 11 that is in the first area 11 a to fall down. These water dropletsreach the upper surface 15 a of each of the heat transfer tubes 15. Thewater droplets that have reached the upper surface 15 a of the heattransfer tube 15 flow along the upper surface 15 a toward the upstreamend 15 b due to the influence of gravity. Most of the water dropletsthat have reached the upstream end 15 b flow to the second area 11 busing the momentum of the water droplets flowing along the upper surface15 a, and flow to the lower portion of the first heat exchanging part10. As the second area 11 b includes no heat transfer tubes 15, thewater droplets flow along the surface of the fin 11, reach the lowerportion of the first heat exchanging part 10, and are drained offwithout stopping. That is, the first heat exchanging part 10 can providethe improved drainage performance, even while using the heat transfertubes 15 having a larger width than height in a cross-sectional shape.

Some of the water droplets that have not flowed from the first area 11 ato the second area 11 b flow along the upstream end 15 b of the heattransfer tube 15 to the lower surface 15 c. The water droplets that haveflowed to the lower surface 15 c of the heat transfer tube 15 stay andgrow on the lower surface 15 c of the heat transfer tube 15, while thesurface tension, the gravity, the static frictional force, and otherforces are balanced. The water droplets expand downward and become moresusceptible to the gravity as the water droplets grow. When the gravityon the water droplets exceeds the component of the forces including thesurface tension in the direction opposite to the gravity direction, thewater droplets are not affected by the surface tension and leave thelower surface 15 c of the heat transfer tube 15. The water droplets thathave left the lower surface 15 c of the heat transfer tube 15 flowdownward along the first area 11 a again and reach the upper surface 15a of the lower heat transfer tube 15. Then, the water droplets repeatthe above-described operations and are finally drained off to the lowerportion of the first heat exchanging part 10.

The water draining action of the second heat exchanging part 20 is alsosimilar to that of the first heat exchanging part 10.

That is, the water droplets adhering to the first area 21 a of each ofthe fins 21 of the second heat exchanging part 20 flow along the surfaceof the fin 21 that is in the first area 21 a to fall down. These waterdroplets reach the upper surface 25 a of each of the heat transfer tubes25. The water droplets that have reached the upper surface 25 a of theheat transfer tube 25 flow along the upper surface 25 a toward theupstream end 25 b due to the influence of gravity. Most of the waterdroplets that have reached the upstream end 25 b flow to the second area21 b using the momentum of the water droplets flowing along the uppersurface 25 a, and flow to the lower portion of the second heatexchanging part 20. As the second area 21 b includes no heat transfertubes 25, the water droplets flow along the surface of the fin 21, reachthe lower portion of the second heat exchanging part 20, and are drainedoff without stopping. That is, the second heat exchanging part 20 canprovide the improved drainage performance, even while using the heattransfer tubes 25 having a larger width than height in a cross-sectionalshape.

Some of the water droplets that have not flowed from the first area 21 ato the second area 21 b flow along the upstream end 25 b of the heattransfer tube 25 to the lower surface 25 c. The water droplets that haveflowed to the lower surface 25 c of the heat transfer tube 25 stay andgrow on the lower surface 25 c of the heat transfer tube 25, while thesurface tension, the gravity, the static frictional force, and otherforces are balanced. The water droplets expand downward and become moresusceptible to the gravity as the water droplets grow. When the gravityon the water droplets exceeds the component of the forces including thesurface tension in the direction opposite to the gravity direction, thewater droplets are not affected by the surface tension and leave thelower surface 25 c of the heat transfer tube 25. The water droplets thathave left the lower surface 25 c of the heat transfer tube 25 flowdownward along the first area 21 a again and reach the upper surface 25a of the lower heat transfer tube 25. Then, the water droplets repeatthe above-described operations and are finally drained off to the lowerportion of the second heat exchanging part 20.

As described above, the heat exchanger 1 according to Embodiment 1includes the fins 11 each having the upstream end 11 c and thedownstream end 11 d in the lateral direction, the fins 21 each havingthe upstream end 21 c and the downstream end 21 d in the lateraldirection, the upstream end 21 c being positioned to face the downstreamend 11 d, the heat transfer tubes 15 each positioned away from theupstream end 11 c by the first predetermined interval and passingthrough the fins 11, and the heat transfer tubes 25 each positioned awayfrom the upstream end 21 c by the second predetermined interval andpassing through the fins 21. The heat transfer tube 15 has the planarupper surface 15 a and the planar lower surface 15 c. The heat transfertube 25 has the planar upper surface 25 a and the planar lower surface25 c. Here, the upper surface 15 a and the upper surface 25 a shall bedefined as a first surface and a second surface, respectively. When theheat transfer tube 15 and the heat transfer tube 25 are viewed in such amanner that the lower surface 15 c is horizontal, in the vertical crosssection perpendicular to the direction in which the heat transfer tube15 passes through the fins 11, the first surface is inclined downwardtoward the upstream end 11 c, the second surface is inclined downwardtoward the upstream end 21 c, the upper end of the heat transfer tube 25is located higher than the lower surface 15 c, and the intersectingpoint A at which the second surface and the extension line of the lowersurface 15 c intersect is located closer to the heat transfer tube 25than is the intersecting point B at which the extension line of thesecond surface and the extension line of the lower surface 25 cintersect.

Consequently, the heat exchanger 1 according to Embodiment 1 can providethe improved drainage performance, even while using the heat transfertubes 15 and 25 each having a larger width than height in across-sectional shape. In the heat exchanger 1 according to Embodiment1, the arrangement relationship between the heat transfer tube 15located upstream of the air flow and the heat transfer tube 25 locateddownstream of the air flow that overlap with each other when the heatexchanger 1 is viewed in the air flow direction can also facilitate heatexchange at the heat transfer tube 25, as described above. Thus, in theheat exchanger 1 according to Embodiment 1, both of drainage performanceand heat transfer performance are improved.

In Embodiment 1, the lower surface 15 c, 25 c of the heat transfer tube15, 25 is positioned to be horizontal. However, without limitation tothis arrangement, the lower surface 15 c, 25 c of the heat transfer tube15, 25 may be positioned to be inclined to the horizontal plane. Whenthe upper surface 15 a, 25 a of the heat transfer tube 15, 25 isinclined downward toward the second area 11 b, 21 b, the drainageperformance can be improved as described above. In addition, when theair is supplied from the fan 501 into the heat exchanger 1 so that theair flows along the lower surface 15 c of the heat transfer tube 15, theheat transfer performance can be improved as described above. However,when the lower surface 15 c, 25 c of the heat transfer tube 15, 25 ispositioned to be inclined downward from the upstream end 15 b, 25 btoward the downstream end 15 d, 25 d, the water droplets that havereached the upstream end 15 b, 25 b from the upper surface 15 a, 25 a ofthe heat transfer tube 15, 25 readily flow to the lower surface 15 c, 25c. Consequently, the improved drainage performance described above isslightly reduced. Thus, it is preferable that the lower surface 15 c, 25c of the heat transfer tube 15, 25 is positioned to be horizontal or tobe inclined downward from the downstream end 15 d, 25 d toward theupstream end 15 b, 25 b. In other words, it is preferable that the lowersurface 15 c, 25 c of the heat transfer tube 15, 25 is positioned to behorizontal or to be inclined downward from the downstream end 11 d, 21 dtoward the upstream end 11 c, 21 c of the fin 11, 12.

In Embodiment 1, the heat transfer tubes 15 and 25 are fitted into therespective notches 12 and 22 of each of the fins 11 and 21, but the fins11 and 21 may have through holes in the fins 11 and 21 so that the heattransfer tubes 15 and 25 are inserted into the respective through holes.This configuration of the heat exchanger 1 enables both of drainageperformance and heat transfer performance to be improved.

In Embodiment 1, the fin 11 and the fin 21 are formed separately, butthe fin 11 and the fin 21 may be integrally formed to form one piece offin. In this case, the heat exchanger 1 is only required to bemanufactured through regarding the virtual straight line extending inthe up-down direction at the position away from the upstream end 25 b ofthe heat transfer tube 25 by the predetermined interval (the secondpredetermined interval) as the downstream end 11 d of the fin 11 and theupstream end 21 c of the fin 21. This configuration of the heatexchanger 1 enables both of drainage performance and heat transferperformance to be improved.

Embodiment 2

In Embodiment 1, the inclination of the lower surface 15 c of the heattransfer tube 15 is the same as that of the lower surface 25 c of theheat transfer tube 25. However, without limitation to thisconfiguration, the inclination of the lower surface 15 c of the heattransfer tube 15 may be different from that of the lower surface 25 c ofthe heat transfer tube 25, to configure the following heat exchanger 1.Note that items not particularly described in Embodiment 2 are similarto those of Embodiment 1 and the same functions or configurations aredescribed with the same reference signs.

FIG. 6 is a front view illustrating a heat exchanger according toEmbodiment 2 of the present invention. FIG. 7 is an enlarged view (frontview) illustrating a main portion of fins of this heat exchanger. FIG. 8is an enlarged view of a main portion of a part of FIG. 6.

FIG. 6 illustrates the heat transfer tubes 15 and 25 in cross section. Ablank arrow shown in each of FIG. 6 and FIG. 8 represents a flowdirection of air to be supplied to the heat exchanger 1 from the fan501. That is, in Embodiment 2, the fan 501 is configured to supply airto the heat exchanger 1 in a substantially horizontal direction. Inother words, the rotary shaft of the fan 501, which is a propeller fan,is positioned in the substantially horizontal direction. In each ofFIGS. 6 to 8, this air flow direction is also represented by an arrow X.An arrow Z shown in each of FIGS. 6 to 8 represents the gravitydirection.

Also in the heat exchanger 1 according to Embodiment 2,the heat transfertubes 15 of the first heat exchanging part 10 and the heat transfertubes 25 of the second heat exchanging part 20, the heat transfer tubes25 being laterally adjacent to the respective heat transfer tubes 15,are arranged in such a manner that the upper end of the heat transfertube 25, and the intersecting points A and B are located in the samemanner as in Embodiment 1 in a vertical cross section perpendicular tothe direction in which the heat transfer tubes 15 pass through the fins11, in other words, in a vertical cross section perpendicular to thedirection in which the heat transfer tubes 25 pass through the fins 21.

More specifically, the upper end (a point C in FIG. 8) of the heattransfer tube 25 is located higher than the lower surface 15 c of theheat transfer tube 15 laterally adjacent to the heat transfer tube 25.The intersecting point A at which the upper surface 25 a of the heattransfer tube 25 and the extension line of the lower surface 15 c of theheat transfer tube 15 intersect is located closer to the heat transfertube 25 than is the intersecting point B at which the extension line ofthe upper surface 25 a and the extension line of the lower surface 25 cof the heat transfer tube 25 intersect. That is, the intersecting pointA is located downstream of the intersecting point B in the air flowdirection. Thus, also in the heat exchanger 1 according to Embodiment 2,the heat transfer tube 15 of the first heat exchanging part 10 and theheat transfer tube 25 of the second heat exchanging part 20, the heattransfer tube 25 being laterally adjacent to the heat transfer tube 15,overlap with each other when the heat exchanger 1 is viewed in the airflow direction in the same manner as in Embodiment 1. In the arrangementrelationship between the heat transfer tube 15 and the heat transfertube 25 that overlap with each other when the heat exchanger 1 is viewedin the air flow direction, the upstream end 25 b of the heat transfertube 25 is located slightly lower than the lower surface 15 c of theheat transfer tube 15.

The heat exchanger 1 according to Embodiment 2 differs from that ofEmbodiment 1 in that the lower surface 25 c of the heat transfer tube 25is inclined downward from the downstream end 21 d toward the upstreamend 21 c of the fin 21, in other words, toward the second area 21 b,which is a water drainage area. That is, the lower surface 25 c of theheat transfer tube 25 is inclined downward toward the upstream end 21 cof the fin 21.

Also in the heat exchanger 1 according to Embodiment 2 thus configured,the water droplets that have reached the upper surface 15 a, 25 a of theheat transfer tube 15, 25 can be drained off to the second area 11 b, 21b including no heat transfer tubes 15, 25, due to the influence ofgravity, in the same manner as in Embodiment 1. Furthermore, in the heatexchanger 1 according to Embodiment 2, the lower surface 25 c of theheat transfer tube 25 is also inclined downward toward the second area21 b. Consequently, the water droplets adhering to the lower surface 25c of the heat transfer tube 25 flow along the lower surface 25 c towardthe upstream end 25 b due to the influence of gravity. Most of the waterdroplets that have reached the upstream end 25 b are drained off to thesecond area 21 b using the momentum of the water droplets flowing alongthe lower surface 25 c. Thus, the heat exchanger 1 according toEmbodiment 2 can provide further improved drainage performance ascompared with the heat exchanger 1 according to Embodiment 1.

The heat exchanger 1 according to Embodiment 2 can provide furtherimproved heat transfer performance as compared with the heat exchanger 1according to Embodiment 1. More specifically, in the heat transfer tube25 according to Embodiment 2, both of the upper surface 25 a and thelower surface 25 c are arranged to be inclined downward in the upstreamdirection of the air flow. Consequently, a plane including a bisector ofan angle formed by the upper surface 25 a and the lower surface 25 c isinclined downward in the upstream direction of the air flow. In otherwords, a center line of the cross section of the heat transfer tube 25is inclined downward in the upstream direction of the air flow in thecross section perpendicular to the direction in which the heat transfertubes 25 pass through the fins 21. Here, as described in Embodiment 1,the air flowing into gaps between the fins 21 of the second heatexchanging part 20 flows more upward than the horizontal direction, andreaches the upstream ends 25 b of the respective heat transfer tubes 25.That is, the heat exchanger 1 according to Embodiment 2 is configured insuch a manner that the center line of the cross section of the heattransfer tube 25 is along the air flow as compared with the heatexchanger 1 according to Embodiment 1. Thus, in the heat exchanger 1according to Embodiment 2, the ventilation resistance when the air flowsaround the heat transfer tube 25 can be further reduced, as comparedwith the heat exchanger 1 according to Embodiment 1. Thus, in the heatexchanger 1 according to Embodiment 2, heat exchange at the heattransfer tube 25 can be further facilitated and the heat transferperformance can be further improved, as compared with the heat exchanger1 according to Embodiment 1.

Embodiment 3

In Embodiment 1 and Embodiment 2, the intersecting point A is locatedcloser to the heat transfer tube 25 than is the intersecting point B.However, without limitation to this configuration, the present inventionmay be also implemented by shifting the arrangement positions of theheat transfer tubes 25 in the heat exchanger 1 according to Embodiment 1and Embodiment 2 upward so that the intersecting point A coincides withthe intersecting point B. Embodiment 3 will be described by illustratingan example in which the arrangement positions of the heat transfer tubes25 in the heat exchanger 1 according to Embodiment 1 are shifted upwardso that the intersecting point A coincides with the intersecting pointB. Note that items not particularly described in Embodiment 3 aresimilar to those of Embodiment 1 or Embodiment 2 and the same functionsor configurations are described with the same reference signs.

FIG. 9 is a front view illustrating a heat exchanger according toEmbodiment 3 of the present invention. FIG. 10 is an enlarged view(front view) illustrating a main portion of fins of this heat exchanger.FIG. 11 is an enlarged view of a main portion of a part of FIG. 9.

FIG. 9 illustrates the heat transfer tubes 15 and 25 in cross section. Ablank arrow shown in each of FIG. 9 and FIG. 11 represents a flowdirection of air to be supplied to the heat exchanger 1 from the fan501. That is, in Embodiment 3, the fan 501 is configured to supply airto the heat exchanger 1 in a substantially horizontal direction. Inother words, the rotary shaft of the fan 501, which is a propeller fan,is positioned in the substantially horizontal direction. In each ofFIGS. 9 to 11, this air flow direction is also represented by an arrowX. An arrow Z shown in each of FIGS. 9 to 11 represents the gravitydirection.

In the heat exchanger 1 according to Embodiment 3, the intersectingpoint A at which the extension line of the upper surface 25 a of theheat transfer tube 25 and the extension line of the lower surface 15 cof the heat transfer tube 15 intersect coincides with the intersectingpoint B at which the extension line of the upper surface 25 a and theextension line of the lower surface 25 c of the heat transfer tube 25intersect.

Also in Embodiment 3, the upper end (a point C in FIG. 11) of the heattransfer tube 25 is located higher than the lower surface 15 c of theheat transfer tube 15 laterally adjacent to the heat transfer tube 25 inthe same manner as in Embodiment 1 and Embodiment 2. The otherconfigurations of the heat exchanger 1 according to Embodiment 3 aresimilar to Embodiment 1.

When the arrangement positions of the heat transfer tubes 25 in the heatexchanger 1 according to Embodiment 1 are shifted upward so that theintersecting point A coincides with the intersecting point B as in theheat exchanger 1 according to Embodiment 3, the heat transfer tube 15and the heat transfer tube 25 that are laterally adjacent to each other,overlap with each other when the heat exchanger 1 is viewed in the airflow direction, in the same manner as in Embodiment 1. In the heattransfer tube 15 and the heat transfer tube 25 that overlap with eachother when the heat exchanger 1 is viewed in the air flow direction, theposition in the up-down direction of the lower surface 25 c of the heattransfer tube 25 coincides with the position in the up-down direction ofthe lower surface 15 c of the heat transfer tube 15.

When the arrangement positions of the heat transfer tubes 25 in the heatexchanger 1 according to Embodiment 2 are shifted upward so that theintersecting point A coincides with the intersecting point B, the heattransfer tube 15 and the heat transfer tube 25 that are laterallyadjacent to each other, overlap with each other when the heat exchanger1 is viewed in the air flow direction, in the same manner as inEmbodiment 2. In the heat transfer tube 15 and the heat transfer tube 25that overlap with each other when the heat exchanger 1 is viewed in theair flow direction, the upstream end 25 b of the heat transfer tube 25is located slightly higher than the lower surface 15 c of the heattransfer tube 15.

Also in the heat exchanger 1 configured as in Embodiment 3, the waterdroplets that have reached the upper surface 15 a, 25 a of the heattransfer tube 15, 25 can be drained off to the second area 11 b, 21 bincluding no heat transfer tubes 15, 25, due to the influence ofgravity, in the same manner as in Embodiment 1 and Embodiment 2. Thus,the heat exchanger 1 according to Embodiment 3 can provide the improveddrainage performance in the same manner as in Embodiment 1 andEmbodiment 2.

In the heat exchanger 1 according to Embodiment 3, the arrangement andorientation of the heat transfer tubes 15 that are adjacent to eachother in the up-down direction in the first heat exchanging part 10 arethe same as those in Embodiment 1 and Embodiment 2. Consequently, theair flowing into gaps between the fins 21 of the second heat exchangingpart 20 flows more upward than the horizontal direction, and reaches theupstream ends 25 b of the respective heat transfer tubes 25. Thus, evenwhen the heat exchanger 1 is configured as in Embodiment 3, sufficientamount of air can flow along the upper surfaces 25 a of the respectiveheat transfer tubes 25 of the second heat exchanging part 20. Thus, alsoin the heat exchanger 1 configured as in Embodiment 3, the heat transferperformance can be improved.

That is, also in the heat exchanger 1 according to Embodiment 3,both ofdrainage performance and heat transfer performance can be improved inthe same manner as in Embodiment 1 and Embodiment 2.

When the arrangement positions of the heat transfer tubes 25 in the heatexchanger 1 according to Embodiment 1 are shifted upward so that theintersecting point A coincides with the intersecting point B, a degreeof overlap between the heat transfer tube 15 and the heat transfer tube25 that are laterally adjacent to each other when the heat exchanger 1is viewed in the air flow direction become the largest as illustrated inFIG. 11 or other figures. For example, when the heat transfer tubeshaving the same shape are used as the heat transfer tube 15 and the heattransfer tube 25, the heat transfer tube 25 is completely hidden behindthe heat transfer tube 15 when the heat exchanger 1 is viewed in the airflow direction as illustrated in FIG. 11 or other figures. Consequently,when the arrangement positions of the heat transfer tubes 25 in the heatexchanger 1 according to Embodiment 1 are shifted upward so that theintersecting point A coincides with the intersecting point B, theventilation resistance can be reduced by increased degree of overlapbetween the heat transfer tube 15 and the heat transfer tube 25, and theheat transfer performance can be improved by reduced amount of theventilation resistance.

Embodiment 4

In Embodiment 1 to Embodiment 3, the heat transfer tube 15, 25 havingthe planar upper surface 15 a, 25 a is used. However, without limitationto this configuration, the present invention may be also implemented byusing the heat transfer tube 15, 25 having a curved upper surface 15 a,25 a. Note that items not particularly described in Embodiment 4 aresimilar to those of any of Embodiment 1 to Embodiment 3 and the samefunctions or configurations are described with the same reference signs.

FIG. 12 is a front view illustrating a heat exchanger according toEmbodiment 4 of the present invention. FIG. 13 is an enlarged view(front view) illustrating a main portion of fins of this heat exchanger.FIG. 14 is an enlarged view of a main portion of a part of FIG. 12.

FIG. 12 illustrates the heat transfer tubes 15 and 25 in cross section.A blank arrow shown in each of FIG. 12 and FIG. 14 represents a flowdirection of air to be supplied to the heat exchanger 1 from the fan501. That is, in Embodiment 4, the fan 501 is configured to supply airto the heat exchanger 1 in a substantially horizontal direction. Inother words, the rotary shaft of the fan 501, which is a propeller fan,is positioned in the substantially horizontal direction. In each ofFIGS. 12 to 14, this air flow direction is also represented by an arrowX. An arrow Z shown in each of FIGS. 12 to 14 represents the gravitydirection.

In Embodiment 1 to Embodiment 3, a plurality of notches 12, into whichthe respective heat transfer tubes 15 are to be inserted, are cut ineach of the fins 11 of the first heat exchanging part 10 at apredetermined tier pitch (space) in the up-down direction. On the otherhand, in Embodiment 4, a plurality of through holes 13, into which therespective heat transfer tubes 15 are to be inserted, are provided ineach of the fins 11 of the first heat exchanging part 10 at apredetermined tier pitch (space) in the up-down direction. Each of thethrough holes 13 has a shape corresponding to an outer shape of the heattransfer tube 15. The upstream end 13 a of the through hole 13 ispositioned away from the upstream end 11 c of the fin 11 by thepredetermined interval (the first predetermined interval). Thedownstream end 13 b of the through hole 13 is also positioned away fromthe downstream end 11 d of the fin 11 by the predetermined interval.

Each of the heat transfer tubes 15 according to Embodiment 4 is insertedinto the corresponding through hole 13 in each of the fins 11, and isprovided to pass through the fins 11 in an arrangement direction ofthese fins 11. The fins 11 and the heat transfer tubes 15 are tightlyintegrated with each other by brazing. Each of these heat transfer tubes15 has a larger width than height in a cross-sectional viewperpendicular to the flow direction of the refrigerant.

The shape of the heat transfer tube 15 will be further described indetail. The heat transfer tube 15 has a curved upper surface 15 aprojecting upward and a planar lower surface 15 c. A distance betweenthe upper surface 15 a and the lower surface 15 c is gradually increasedfrom the upstream end 11 c toward the downstream end 11 d of the fin 11at a portion (a portion of the fin 11 that is close to the upstream end11 c) that is upstream of the lateral center position in the air flow,when the heat transfer tube 15 is viewed in a cross-sectional viewperpendicular to the flow direction of the refrigerant. In other words,when a tangent plane of the upper surface 15 a is defined as a tangentplane 17, a distance between the tangent plane 17 and the lower surface15 c is gradually increased from the upstream end 11 c toward thedownstream end 11 d of the fin 11. Note that, the lower surface 15 c ofthe heat transfer tube 15 is substantially horizontal. That is, thetangent plane 17 is inclined downward toward the upstream end 11 c ofthe fin 11.

Here, the tangent plane 17 corresponds to a first surface of the presentinvention.

As described above, the upstream end 13 a of the through hole 13 of thefin 11, into which the heat transfer tube 15 is to be inserted, ispositioned away from the upstream end 11 c of the fin 11 by thepredetermined interval (the first predetermined interval). Thedownstream end 13 b of the through hole 13 of the fin 11, into which theheat transfer tube 15 is to be inserted, is positioned away from thedownstream end 11 d of the fin 11 by the predetermined interval. In thestate in which the heat transfer tube 15 is fitted into the fin 11, theupstream end 15 b of the heat transfer tube 15 is also positioned awayfrom the upstream end 11 c of the fin 11 by the predetermined interval(the first predetermined interval). In the state in which the heattransfer tube 15 is fitted into the fin 11, the downstream end 15 d ofthe heat transfer tube 15 is also positioned away from the downstreamend 11 d of the fin 11 by the predetermined interval.

Thus, in Embodiment 4, the second area 11 b in which no heat transfertubes 15 is positioned in each of a portion close to the upstream end 11c and a portion close to the downstream end 11 d of the fin 11. Theboundary between the first area 11 a and the second area 11 b that isclosed to the upstream end 11 c is a virtual straight line connectingthe upstream ends 13 a of the respective through holes 13 provided inparallel in the up-down direction, in other words, a virtual straightline connecting the upstream ends 15 b of the respective heat transfertubes 15 arranged in parallel in the up-down direction. In addition, theboundary between the first area 11 a and the second area 11 b that isclose to the downstream end 11 d is a virtual straight line connectingthe downstream ends 13 b of the respective through holes 13 provided inparallel in the up-down direction, in other words, a virtual straightline connecting the downstream ends 15 d of the respective heat transfertubes 15 arranged in parallel in the up-down direction.

The second heat exchanging part 20 according to Embodiment 4 has asimilar configuration as the first heat exchanging part 10 according toEmbodiment 4. More specifically, a plurality of through holes 23, intowhich the respective heat transfer tubes 25 are to be inserted, areprovided in each of the fins 21 of the second heat exchanging part 20 ata predetermined tier pitch (space) in the up-down direction. Each of thethrough holes 23 has a shape corresponding to an outer shape of the heattransfer tube 25. The upstream end 23 a of the through hole 23 ispositioned away from the upstream end 21 c of the fin 21 by thepredetermined interval (the second predetermined interval). Thedownstream end 23 b of the through hole 23 is also positioned away fromthe downstream end 21 d of the fin 21 by the predetermined interval.

Each of the heat transfer tubes 25 according to Embodiment 4 is insertedinto the corresponding through hole 23 in each of the fins 21, and isprovided to pass through the fins 21 in an arrangement direction ofthese fins 21. The fins 21 and the heat transfer tubes 25 are tightlyintegrated with each other by brazing. Each of these heat transfer tubes25 has a larger width than height in a cross-sectional viewperpendicular to the flow direction of the refrigerant.

The shape of the heat transfer tube 25 will be further described indetail. The heat transfer tube 25 has a curved upper surface 25 aprojecting upward and a planar lower surface 25 c. A distance betweenthe upper surface 25 a and the lower surface 25 c is gradually increasedfrom the upstream end 21 c toward the downstream end 21 d of the fin 21at a portion (a portion of the fin 21 that is close to the upstream end21 c) that is upstream of the lateral center position in the air flow,when the heat transfer tube 25 is viewed in a cross-sectional viewperpendicular to the flow direction of the refrigerant. In other words,when a tangent plane of the upper surface 25 a at a portion (a portionof the fin 21 that is close to the upstream end 21 c) that is upstreamof the lateral center position in the air flow is defined as a tangentplane 27, a distance between the tangent plane 27 and the lower surface25 c is gradually increased from the upstream end 21 c toward thedownstream end 21 d of the fin 21. Note that, the lower surface 25 c ofthe heat transfer tube 25 is substantially horizontal. That is, thetangent plane 27 is inclined downward toward the upstream end 21 c ofthe fin 21.

Here, the tangent plane 27 corresponds to a second surface of thepresent invention.

As described above, the upstream end 23 a of the through hole 23 of thefin 21, into which the heat transfer tube 25 is to be inserted, ispositioned away from the upstream end 21 c of the fin 21 by thepredetermined interval (the second predetermined interval). Thedownstream end 23 b of the through hole 23 of the fin 21, into which theheat transfer tube 25 is to be inserted, is positioned away from thedownstream end 21 d of the fin 21 by the predetermined interval. In thestate in which the heat transfer tube 25 is fitted into the fin 21, theupstream end 25 b of the heat transfer tube 25 is also positioned awayfrom the upstream end 21 c of the fin 21 by the predetermined interval(the second predetermined interval). In the state in which the heattransfer tube 25 is fitted into the fin 21, the downstream end 25 d ofthe heat transfer tube 25 is also positioned away from the downstreamend 21 d of the fin 21 by the predetermined interval.

Thus, in Embodiment 4, the second area 21 b in which no heat transfertubes 25 are provided is positioned in each of a portion close to theupstream end 21 c and a portion close to the downstream end 21 d of thefin 21. The boundary between the first area 21 a and the second area 21b that is close to the upstream end 21 c is a virtual straight lineconnecting the upstream ends 23 a of the respective through holes 23provided in parallel in the up-down direction, in other words, a virtualstraight line connecting the upstream ends 25 b of the respective heattransfer tubes 25 arranged in parallel in the up-down direction. Inaddition, the boundary between the first area 21 a and the second area21 b that is close to the downstream end 21 d is a virtual straight lineconnecting the downstream ends 23 b of the respective through holes 23provided in parallel in the up-down direction, in other words, a virtualstraight line connecting the downstream ends 25 d of the respective heattransfer tubes 25 arranged in parallel in the up-down direction.

In the heat exchanger 1 thus configured, the water droplets that havereached the upper surface 15 a, 25 a of the heat transfer tube 15, 25can be drained off to the second areas 11 b, 21 b including no heattransfer tubes 15, 25, due to the influence of gravity, in the samemanner as in Embodiment 1 to Embodiment 3. Thus, the heat exchanger 1according to Embodiment 4 can also provide the improved drainageperformance in the same manner as in Embodiment 1 to Embodiment 3.

The above-described tangent plane 17 of the heat transfer tube 15 of thefirst heat exchanging part 10 is positioned to have the same inclinationas the upper surface 15 a of each of Embodiment 1 to Embodiment 3, andthe above-described tangent plane 27 of the heat transfer tube 25 of thesecond heat exchanging part 20 is positioned to have the sameinclination as the upper surface 25 a of each of Embodiment 1 toEmbodiment 3. Thereby, the drainage performance can be improved in thesame manner as in Embodiment 1 to Embodiment 3.

That is, the tangent plane 17, 27 of the heat transfer tube 15, 25 isonly required to be inclined downward from the downstream end 11 d, 21 dtoward the upstream end 11 c, 21 c of the fin 11, 21. The upper end (apoint C in FIG. 14) of the heat transfer tube 25 is only required to bepositioned higher than the lower surface 15 c of the heat transfer tube15 laterally adjacent to the heat transfer tube 25. An intersectingpoint A at which the tangent plane 27 of the heat transfer tube 25 andthe extension line of the lower surface 15 c of the heat transfer tube15 intersect is only required to coincide with an intersecting point Bat which the tangent plane 27 and the extension line of the lowersurface 25 c of the heat transfer tube 25 intersect, or is locatedcloser to the heat transfer tube 25 than is the intersecting point B.

Such a configuration enables the arrangement positions of the heattransfer tubes 15 and 25 to be similar to those of Embodiment 1 toEmbodiment 3. The air flow in the first heat exchanging part 10 and thesecond heat exchanging part 20 can also be similar to that in Embodiment1 to Embodiment 3. More specifically, the air supplied from the fan 501into the first heat exchanging part 10 in the substantially horizontaldirection flows in the substantially horizontal direction along thelower surface 15 c in the vicinity of the lower surface 15 c of the heattransfer tube 15 positioned substantially horizontally. The air flowsmore upward than the horizontal direction in the vicinity of the uppersurface 15 a at a portion that is upstream of the lateral centerposition in the air flow. Consequently, the air flowing into gapsbetween the heat transfer tubes 15 adjacent to each other in the up-downdirection flows more upward than the horizontal direction as inEmbodiment 1 to Embodiment 3. Thus, the air flowing into gaps betweenthe fins 21 of the second heat exchanging part 20 flows more upward thanthe horizontal direction, and reaches the upstream ends 25 b of therespective heat transfer tubes 25. As in Embodiment 1 to Embodiment 3,the sufficient amount of air can flow in the vicinity of the uppersurface 25 a of the heat transfer tube 25 located at a position behindthe dead water region. In the case of an existing art, the air velocityis reduced in the vicinity of the upper surface 25 a of the heattransfer tube 25, which is located behind the dead water region. Thisair flow can facilitate heat exchange between the air and the uppersurface 25 a.

REFERENCE SIGNS LIST

Heat exchanger, 10 First heat exchanging part, 11 Fin, 11 a First area,11 b Second area, 11 c Upstream end, 11 d Downstream end, 12 Notch, 12 aUpstream end, 12 b Opening, 13 Through hole, 13 a Upstream end, 13 bDownstream end, 15 Heat transfer tube, 15 a Upper surface, 15 b Upstreamend, 15 c Lower surface, 15 d Downstream end, 16 Refrigerant passage, 17Tangent plane, 20 Second heat exchanging part, 21 Fin, 21 a First area,21 b Second area, 21 c Upstream end, 21 d Downstream end, 22 Notch, 22 aUpstream end, 22 b Opening, 23 Through hole, 23 a Upstream end, 23 bDownstream end, 25 Heat transfer tube, 25 a Upper surface, 25 b Upstreamend, 25 c Lower surface, 25 d Downstream end, 26 Refrigerant passage, 27Tangent plane, 100 Refrigeration cycle apparatus, 200 Compressor, 300Condenser, 301 Fan, 400 Expansion mechanism, 500 Evaporator, 501 Fan

1. A heat exchanger, comprising: a first fin having a first end and asecond end in a lateral direction; a second fin having a third end and afourth end in the lateral direction, the third end being positioned toface the second end; a first heat transfer tube positioned away from thefirst end by a first predetermined interval and passing through thefirst fin; and a second heat transfer tube positioned away from thethird end by a second predetermined interval and passing through thesecond fin, the first heat transfer tube having a planar or curved firstupper surface and a planar first lower surface, the second heat transfertube having a planar or curved second upper surface and a planar secondlower surface, when the first upper surface is defined as a firstsurface in a case where the first upper surface has a planar shape, atangent plane of the first upper surface is defined as a first surfacein a case where the first upper surface has a curved shape, the secondupper surface is defined as a second surface in a case where the secondupper surface has a planar shape, and a tangent plane of the secondupper surface is defined as a second surface in a case where the secondupper surface has a curved shape, and when the first heat transfer tubeand the second heat transfer tube are viewed in such a manner that thefirst lower surface is horizontal, in a vertical cross sectionperpendicular to a direction in which the first heat transfer tubepasses through the first fin, the first surface being inclined downwardtoward the first end, the second surface being inclined downward towardthe third end, an upper end of the second heat transfer tube beinglocated higher than the first lower surface, an intersecting point A atwhich the second surface or an extension line of the second surface andan extension line of the first lower surface intersect being locatedcloser to the second heat transfer tube than is an intersecting point Bat which the second surface or the extension line of the second surfaceand an extension line of the second lower surface intersect.
 2. The heatexchanger of claim 1, wherein when the first heat transfer tube and thesecond heat transfer tube are viewed in such a manner that the firstlower surface is horizontal, the second lower surface is inclineddownward toward the third end.
 3. (canceled)
 4. A refrigeration cycleapparatus, comprising: the heat exchanger of claim 1; and a fanconfigured to supply air to the heat exchanger from the first end alongthe first lower surface, the heat exchanger being installed in such amanner that the first surface is inclined downward toward the first end,and the second surface is inclined downward toward the third end.
 5. Therefrigeration cycle apparatus of claim 4, wherein the heat exchanger isinstalled in such a manner that the first lower surface is horizontal oris inclined downward toward the first end.